Although boys have engaged historically in more drug use than girls, recent data reveal few gender differences. Gender differences exist in risk factors for adolescent substance use, however. Because of the singular pressures that girls face in their relationships with their mothers during adolescence, girls may profit greatly from prevention programs that develop and strengthen positive connections with their mothers. Yet formidable barriers to implementing family-centered strategies exist. For family intervention to reach and impact large numbers of people, it must be delivered with fidelity; be engaging, affordable, and flexible; meet tight scheduling demands; and reflect participant families' cultures. Computer-mediated intervention fits these requirements. The planned investigation will engage a sample of poor, minority girls and their mothers who live in New York City Housing Authority units. We will deliver gender-specific drug abuse intervention (GSI) via CD-ROM to girls and their mothers on-site at their housing developments. Study aims are: to develop and test the efficacy of GSI compared to a no-intervention control arm in preventing girls' substance use; to test the efficacy of GSI to improve girls' mother-daughter affective quality, coping, refusal skills, mood management, conflict resolution, problem solving, self-efficacy, body esteem, normative beliefs, social supports, and mother-daughter communication and relate these mediating factors to girls' substance use behavior; to test the efficacy of GSI to improve mothers' family rituals, rules against substance use, child management, mother-daughter affective quality, and communication with their daughters and relate these mediating factors to girls' substance use behavior; to test the effects of dose on participants' outcomes; to determine if intervention effects differ for ethnic-racial groups; and to quantify the costs of intervention development and delivery. The study will occur in three phases. In a 12-month preparation phase, we will refine and complete intervention and measurement protocols, assign housing projects to study arms, recruit participants, and pretest. A 12-month implementation phase includes intervention delivery, process data collection, booster 1 development, and posttest. Follow-up in the last 36 months will involve longitudinal measurements of girls and mothers, booster 1 delivery, booster 2 development and delivery, and data analyses.